A new study in the medical journal Chest reports that people who live near certain types of asbestos-containing rock formations are at higher risk of developing pleural plaques and malignant mesothelioma. Pleural plaques are patches of hardened tissue that form on the lining of the lung. Pleural mesothelioma is a cancer of the lining of the lungs.

Malignant mesothelioma is nearly always caused by inhaling asbestos fibers.  Most people are exposed to asbestos from work in industries that use asbestos. But what about people who develop mesothelioma in rural areas that do not have industries that use asbestos?

Researchers in Turkey and Belgium set out to test whether there was a correlation between malignant mesothelioma and pleural plaques and the proximity of the patients’ birthplace to ophiolite formations  in the province of Silvas, Turkey.

An ophiolite is a section of the Earth’s oceanic rocky crust that gets pushed up and exposed above sea level. Ophiolite rock formations are found in California and Oregon, in Quebec, Canada as well as in Mediterranean countries such as Greece, Corsica. Two types of naturally occurring asbestos— chrysotile and tremolite asbestos —are often found in ophiolites.

A high rate of mesothelioma has been reported in certain areas of Turkey . The area of Turkey that researchers focused on is not industrialized so exposure to asbestos can be assumed to be from naturally occurring asbestos.

The researchers identified 233 patients diagnosed with malignant mesothelioma or pleural plaques between 2000 and 2010 from a cancer registry and hospital records. They also identified 300 patients diagnosed with breast cancer or prostate cancer. They then calculated the proximity of each patient’s birthplace to ophiolite rock formations.

The researchers found that the 100 patients with malignant mesothelioma and 133 patients with pleural plaques were born significantly nearer ophiolites than patients with breast cancer or prostate cancer.  They conclude that there is an association between occurrence of mesothelioma and pleural plaques and the proximity of the subject’s birthplace to ophiolites.

In the United State, approximately 2,500 to 3,000 people a year are diagnosed with mesothelioma. Many develop pleural plaques initially before they are diagnosed with the disease. Most mesothelioma patients were exposed to asbestos in a workplace decades ago. It typically takes 30 to 50 years before symptoms of asbestos disease appear.

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